@kirk said in Alternative Electrolytes:
I am a big fan of this type of electrolyte engineering! The viscosity can also become an issue with this sort of approach too, no? (You are from now the FBRC viscosity expert ) I see in that paper though they only cycle up to 0.5 M [Fe], which is quite low in terms of energy density (~8 Wh/L if I'm not mistaken). But it seems solid enough to at least test in the development kit as an exercise. Also a huge confidence boost that you were able to reproduce it and make it plate on grafoil!
Haha I certainly don't feel like much of an expert. Viscosity does become an issue, especially with WISE electrolytes. Actually @danielfp248 if you end up trying out the MgCl2 work, you'll notice that the electrolyte is almost oily. The slurries Savinell and Wainright were working with are even more viscous - something like mayo. I don't remember the exact numbers but I'm happy to point you to more papers if you're interested!
@danielfp248 said in Alternative Electrolytes:
I see big increases in ohmic resistance as a function of time, but I don't see any iron oxides forming on the cathode or on the membrane. I don't see full dissolution of the plated metal though, so I bet it has something to do with the oxidation of that metallic deposit (since probably some Fe+Zn alloy is depositing anyway).
Luckily the oxides don't tend to form in acidic conditions (see the Pourbaix diagram - the phase diagram of stable iron species under varying pH and potential). But HER is more prevalent under acidic conditions. I'm interested in the Zn/Fe half cells though - do you notice any galvanic corrosion/passive loss after you charge the cells? Pourbaix diagrams are an excellent tool for designing thermodynamically possible redox couples. Which leads me to...
@kirk said in Alternative Electrolytes:
would love to see it if you're able to share - it's one of my concerns with iodine chemistries at scale (avoiding artisanal iodine production from seaweed).
I'll let you know when I actually churn out the draft! Might be a bit, but in a nutshell, the low cost (redox active materials under ~$3/kWh) and low criticality (generally abundant and decentralized) aren't too surprising: mostly cells using Fe/Mn/Zn and/or air redox couples meet these criteria. Exact redox couples + electrolyte conditions vary but are based on Pourbaix diagrams.
